Alternating electric current rectifier of the selenium type



Patented Apr. 14, 1942 ALTERNATING ELECTRIC CURRENT RECTI- FIER OF THE SELENIUM TYPE Leslie Ernest Thompson and Alexander Jenkins,

London, England, assignors, by memo assignments, to The Union Switch and Signal Company; Swissvale, Pa., a corporation of Pennsylvania No Drawing. Application October 26, 1940, Se-

il-igaNo. 363,010. In Great Britain October 13,

2 Claims. (Cl. 175-366) This invention relates to alternating electric current rectifiers of the selenium type comprising a base plate or support provided with a layer or coating of selenium which may contain other substances or compounds of selenium, a counter electrode being applied to the surface of the selenium layer.

The invention further relates to rectifiers of the character above indicated in which a counter electrode is utilised composed principally of tin, cadmium or an alloy oi these metals sprayed or otherwise deposited on the surface of the selenium layer or coating.

According to the present invention the counter electrode contains a relatively .small quantity of thallium added to the metal or alloy of which the counter electrode is composed as a result of which the ultimate resistance characteristics of the rectifier are found to be considerably improved.

The invention is of particular advantage in cases in which an electric forming process is tioned which may evidently be varied without.

exceeding the scope of the invention.

Having now described our invention, what we 7 claim as new and desire to secure by Letters Patent is:

1. An alternating electric current rectifier of the kind described comprising a base plate provided with a layer of selenium and a counter electrodecomposed principally of tin, cadmium or an alloy of these metals sprayed or otherwise deposited on the surface of the selenium layer or coating in which the counter electrode contains a relatively small quantity of thallium added to the metal or alloy of which the counter electrode is composed, for the purpose specified.

2. A rectifier as claimed in claim 1 in which the counter electrode is composed of a tin-cadmium alloy containing approximately 0.1% of thallium added thereto, for the purpose specified.

LESLIE ERNEST THOMPSON. ALEXANDER JENKINS. 

